Effect of lidocaine on atrioventricular response via the accessory pathway in patients with Wolff-Parkinson-White syndrome.

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Abstract
Electrophysiologic effects of i.v. lidocaine were evaluated in 10 patients with Wolff-Parkinson-White (WPW) syndrome during atrial fibrillation (AF) (8 of 10) or programmed atrial stimulation (9 of 10). The shortest RR intervals during AF were 190-415 ms (mean 271.8 .+-. 64.5 ms) before lidocaine and decreased to 250.0 .+-. 85.4 ms (range 180-435 ms, P = NS [not significant]) after the drug. In 6 of 8 patients, the shortest RR interval decreased and in the remaining 2 patients it increased by 20 ms after lidocaine. After lidocaine, the average RR intervals during AF for all 8 patients decreased from 351.1 .+-. 45.9 ms to 335.6 .+-. 68.0 ms (P = NS). After lidocaine, the RR interval shortened in 5 of 8 patients, lengthened in 2 and did not change in 1. In 2 of 8 patients, acceleration of ventricular rate after lidocaine was accompanied by hemodynamic deterioration, necessitating DC cardioversion in 1. The control effective refractory period of the accessory pathway (ERP-AP) was 300 ms or less in all patients. Lidocaine prolonged this variable in only 1 case. In the remaining patients, after lidocaine the ERP-AP either shortened (2 of 9), did not change (2 of 9) or atrial refractoriness precluded its determination. During incremental pacing, the atrial cycle length that produced block in the AP shortened in 5 patients, lengthened in 1 and did not change in the others. In patients with WPW syndrome and relatively short ERP-AP (i.e., .ltoreq. 300 ms), lidocaine generally has no significant effect or produces acceleration of ventricular response during AF. In patients with AF and a rapid ventricular rate due to antegrade conduction over the AP, lidocaine is unlikely to have beneficial effects and may be deleterious.